The present invention relates to a vane compressor adapted for use in air conditioning systems for automotive vehicles or like systems to compress a fluid such as a refrigerant.
A vane compressor for use in an air conditioner for automotive vehicles is already known, e.g. from U.S. Pat. No. 3,834,846 issued Sept. 10, 1974, which is of the type including a rotary shaft arranged to be rotated by an associated prime mover; a rotor secured to the rotary shaft for rotation in unison therewith, the rotor having a plurality of axial slits formed in its outer peripheral surface; a plurality of vanes radially movably received in the axial slits; and a housing within which the rotor and the vanes are accommodated, the rotor, the vanes and the housing cooperating to define pump working chambers between them, wherein a refrigerant pumping action is carried out by the rotation of the rotor.
According to the vane compressor of the above type, rotation of the rotor causes the volumes of the pump working chambers to increase for suction of refrigerant into them and decrease for compression of the sucked refrigerant.
The discharge rate, i.e., discharge amount per unit time of compressed refrigerant from the compressor of this type depends upon the r.p.m. of the rotor. More specifically, a decrease in the rotational speed or r.p.m. of the rotor causes a corresponding decrease in the discharge rate of compressed refrigerant, whereas an increase in the r.p.m. causes a corresponding increase in the above discharge rate. While the rotor is rotated at a constant speed, the discharge rate is kept at a substantially constant value. However, in an air conditioning system for automotive vehicles, usually the rotor of the refrigerant compressor is connected to an engine output shaft of the vehicle, on which the system is installed, for rotation in unison with the rotation of the engine output shaft. However, it goes without saying that the engine r.p.m. largely changes. Upon a change in the engine r.p.m., the discharge rate of the compressor changes correspondingly, to cause fluctuation of the refrigerating capacity of the air conditioning system, making it difficult to obtain a desired discharge air temperature. To avoid such change in the discharge rate of the compressor, it has been proposed to interpose speed regulating means between the engine output shaft and the rotor, to keep the rotational speed of the rotor substantially constant. However, such conventional constant speed regulating means are very complicated in structure and unsuitable for installment in an automotive vehicle due to their large sizes. Further, such regulating means are rather expensive.